Calling my babies your babies

My MIL is really starting to piss me off!! I nicknamed my unborn baby squishy and then when I found found im having twins, they became squishies, now every time my MIL talks to me or my husband and more so now since we've announced on Facebook, she calls them HER squishies and it pisses me off because they're not yours, they're mine and my husbands (her son)! I get they're her grandchildren, but this isn't her first grandbaby, I know if I say something to my husband he'll get pissed off at me, it also makes me mad she is using my nicknames for my children 😡😡😡